Solvent molecules interact with a solute through various intermolecular forces. Here we employed a potential energy surface (PES) analysis to interpret the solvent‐induced variations in the strengths of dative (Me3NBH3) and ionic (LiCl) bonds, which possess both ionic and covalent (neutral) characteristics. The change of a bond is driven by the gradient (force) of the solvent‐solute interaction energy with respect to the focused bond length. Positive force shortens the bond length and increases the bond force constant, leading to a blue‐shift of the bond stretching vibrational frequency upon solvation. Conversely, negative force elongates the bond, resulting in a reduced bond force constant and red‐shift of the stretching vibrational frequency. The different responses of Me3NBH3 and LiCl to solvation are studied with valence bond (VB) theory, as Me3NBH3 and LiCl are dominated by the neutral covalent VB structure and the ionic VB structure, respectively. The dipole moment of an ionic VB structure increases along the increasing bond distance, while the dipole moment of a neutral covalent VB structure increases with the decreasing bond distance. The roles of the dominating VB structures are further examined by the geometry optimizations and frequency calculations with the block‐localized wavefunction (BLW) method.

中文翻译：

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溶剂对配位键和离子键强度的影响：电位分析和价键 (VB) 计算的统一理论


溶剂分子通过各种分子间力与溶质相互作用。在这里，我们采用势能表面（PES）分析来解释溶剂引起的配位（Me3NBH3）和离子（LiCl）键强度的变化，这些键同时具有离子和共价（中性）特征。键的变化是由溶剂-溶质相互作用能相对于聚焦键长的梯度（力）驱动的。正力会缩短键长并增加键力常数，导致溶剂化时键拉伸振动频率发生蓝移。相反，负力会拉长键，导致键力常数减小和拉伸振动频率红移。利用价键（VB）理论研究了Me3NBH3和LiCl对溶剂化的不同反应，因为Me3NBH3和LiCl分别以中性共价VB结构和离子VB结构为主。离子型VB结构的偶极矩随着键距的增加而增加，而中性共价VB结构的偶极矩随着键距的减小而增加。通过使用块局域波函数 (BLW) 方法进行几何优化和频率计算，进一步检验了主要 VB 结构的作用。